WO97/19382 describes a progressive multifocal lens that is used as a spectacle lens suitable for correction of presbyopia or the like. In this progressive multifocal lens, a progressive surface conventionally attached to the object-side surface is provided on the eye-side surface. Accordingly, since the object-side surface can be a spherical surface with a constant base curve, it becomes possible to prevent the variations in magnification due to a shape factor, to reduce the difference in magnification between a distance portion and a near portion, and to suppress the variations in magnification in the progressive portion. Therefore, it is possible to reduce the image sway or distortion due to the difference in magnification, thereby providing a progressive multifocal lens that provides a comfortable field of view. In the progressive multifocal lens described in WO97/19382, it becomes possible to combine the progressive surface and the toric surface for astigmatism correction on the eye-side surface using a combination expression, thereby reducing the image sway or distortion even in a progressive multifocal lens for astigmatism correction.
WO97/19383 describes a multifocal lens for spectacles that has visual field portions being different in power, such as a distance portion and a near portion. In this multifocal lens, the difference between the average surface power of the distance portion and the average surface power of the near portion on the object-side surface is set to be numerically smaller than a predetermined addition power, and the average surface power of the distance portion and the average surface power of the near portion on the eye-side surface are adjusted, thereby providing a multifocal lens for spectacles with the predetermined addition power. It becomes possible to adjust the average surface power of the object-side surface such that the difference in magnification between the distance portion and the near portion is reduced, and to reduce the difference in the average surface power of the object-side surface. Therefore, it is possible to provide a multifocal lens that has less sway or distortion of images due to the difference in magnification, and obtains a comfortable field of view with improved astigmatism, a wide range of distinct vision, less image sway, and the like.
JP-A-2003-344813 describes a double-sided aspheric progressive power lens that reduces the difference in magnification of images between a distance portion and a near portion, allows satisfactory vision correction with reference to a prescription value, and provides an effective wide field of view with less distortion when wearing. For this reason, in JP-A-2003-344813, when the surface power in the horizontal direction and the surface power in the vertical direction at a distance portion power measurement position F1 in a first refractive surface on the object-side surface are respectively DHf and DVf, and the surface power in the horizontal direction and the surface power in the vertical direction at a near power measurement position N1 in the first refractive surface are respectively DHn and DVn, the relational expressions DHf+DHn<DVf+DVn and DHn<DVn are satisfied. The surface astigmatism components at the positions F1 and N1 on the first refractive surface are balanced with a second refractive surface on the eye-side surface, and the distance portion power and the addition power based on a prescription value are given with the combination of the first and second refractive surfaces.
JP-A-2004-004436 describes a progressive power lens that can reduce image distortion or blurring inherent in the progressive power lens and can improve wearability. For this reason, in JP-A-2004-004436, a double-sided progressive lens with both the outer surface and the inner surface are progressive surfaces is prepared, the surface addition power of the outer surface is made negative, and the shape of the progressive surface is designed such that the average surface power distribution of the outer surface and the inner surface are made similar.
According to these techniques, the performance of the progressive power lens is being improved, but there are still users who may not be compatible with the characteristics of the progressive power lens, in particular, sway. Thus, there is demand for further improvement.